Process for scale inhibition

Abstract

Copolymers of acrylic acid and methyl acrylate are prepared which are stable against precipitation in waters containing calcium even at a pH of 10 and at elevated temperatures and are especially useful in inhibiting the deposition of calcium from waters containing calcium, in underground formations, in cooling waters and other processes where it is desirable to prevent calcium deposits on metal surfaces or other surfaces in contact with water containing calcium.

The invention is hereby claimed as follows: 
     
       1. A process for preventing scale deposits from the class consisting of calcium sulfate and calcium carbonate and mixtures thereof from water containing said scale forming chemicals and sodium chloride which consists essentially in adding to said water an effective scale inhibiting amount of a copolymer of acrylic acid and methyl acrylate having a molecular weight within the range of 6,000 to 8,000 and obtained by copolymerizing acrylic acid and methyl acrylate using a molar ratio of acrylic acid to methyl acrylate of 4:1 to 5:1, said copolymer of acrylic acid and methyl acrylate being stable at a pH up to at least pH 10 over a period of at least one hour at temperatures of at least 160° F. against precipitation at 1% by weight dosage in a 5% by weight sodium chloride aqueous brine containing 5000 mg/l of calcium, calculated as calcium carbonate. 
     
     
       2. A process as claimed in claim 1 in which said copolymer is added to water in an injection well used to force oil from underground formations to one or more producing wells in a waterflood system. 
     
     
       3. A process as claimed in claim 1 in which said copolymer is added to cooling water containing said scale forming chemicals. 
     
     
       4. A process as claimed in claim 1 in which the calcium concentration in said water is at least 3600 mg/l, calculated as calcium carbonate.